Sensitized photographic emulsion



April 1945- B. H. CARROLL ET AL 2,373,659

SENS ITI ZED PHOTOGRAPHIC EMULSION Filed Oct. 5, 1942 FIG.1.

A 3, 3' DIETHYL- 9- METHYLSELENACARBOCYANINE BROMIDE B 3, 3 DIETHYL- 9- METHYLSELENA CARBOCYANINE BROMIDE WITH P- METHOXYACETOPHENONE FIG. 2.

C 3, 3'- DIETHYL- 9-METHYLSELENACARBOCYANINE BROMIDE D 3, 3" DIETHYL-S METHYLSELENACARBOCYANINE BROMIDE WITH O-HYDROXYACETOPHENONE BURT H. CARROLL JOHN SPENCE INVENTORS reduces the pAg and graphic silver halide emulsion I Patented Apr. 17, 1945 PATENT OFFICE J 2,373,859 SENSITIZED PHOTOGRAPHIC EMULSION Burt H. Carroll and John Spence, Rochester, N. Y.,

assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application October 5, 1942, Serial No. 460,788

12 Claims.

This invention relates to sensitized photo-- graphic emulsions and more particularly to spec traliy (optically) sensitized emulsions.

It is known that the distribution of spectral sensitivity of certain spectrally sensitized emulsions can be altered and an increase of sensitivity obtained in some spectral region, by incorporating certain additional sensitizing dyes in the spectrally sensitized emulsions. (See United States Patents 2,158,882, dated May 16, 1939, and 2,159,565, dated May 23, 1939.) The effect thus obtained has come to be known as supersensitization. Supersensitization of certain spectrally sensitized emulsions can also be effected by incorporating certain substantially colorless heterocyclic bases in the spectrally sensitized emulsions. (See United States Patent 2,177,635, dated October 31, 1939.) Supersensitization differs from hypersensitization which involves treatment of finished films of plates, an operation which normally increases the pH of the emulsions with consequent decreased stability.

We have now found a new method for supersensitizing spectrallysensitized emulsions, which not only does not reduce the stability of the emulsions, but is especially valuable as a means of giving panchromatic sensitized emulsions of high speed and exceptionally good color balance.

It is, accordingly,an object of our invention to provide new supersensitized photographic emulsions. A further object is to provide a processfor preparing such emulsions. Still other objects will become apparent hereinafter.

In accordance with the invention, a photospectrally sensitized with a cyanine or merocyanine dye is supersensitized by incorporating in the emulsion an aromatic ketone selected from those which can be represented by the following general formula:

wherein It represents an aryl group which may carry simple substituents, e. g. chlorine atoms, alkoxy groups or hydroxy groups, and R represents an organic radical, such as an alkyl' group, e. 3. methyl, chloromethyl, ethyl or benzyl or an aryl group, e. g. phenyl, hlorophenyl, etc., and n and n each represent a positive integar of from one to two except that n and n do not both represent two at the same time. Ketones containing strongly electronegative groups, such as CN, N02 or 80:11 (or its salt forms) are advantageously avoided. Exemplary of the aromatic ketones which are advantageously employed are the following:

10 Benzal acetone p-Ethoxyacetophenone. p-Hydroxybenzalac'etone Benzophenone o-Hydroxyacetcphenone Acetylacetophenone Benzoylacetophenone.

The most eflicacious of the aromatic ketones are those of the following general formula:

wherein It represents an alkyl group of the formula CnH2n+l (wherein n represents a positive integer) or an aryl group of the benzene series, represents an alkyl group of the formula CnH2n+i (wherein n represents a positive integer) and the OR group is in the ortho or para position with respect to the CO-R group.

Another group of aromatic ketones of high but lesser efllcacy than the aforementioned group is that group which can be represented by the following general formula:

wherein R represents an alkyl group of the formula CnH21t+1 (Whe1'ein n represents a positive integer) or an aryl group of the benzene series.

Several strong supersensitizers are among the group of aromatic ketones which can be represented by the following general formula:

supersensitize in accordance with the invention fall within a definite range of solubility in gelatin. For this purpose solubility is defined by the appearance of optical homogeneity in gelatin sheets containing the aromatic ketone. The solubility determination can be carried out as follows: the aromatic ketone dissolved in the minimum amount of methyl or ethyl alcohol or acetone is added to an aqueous gelatin solution (70 g. of gelatin per 1000 cc. of water) and the resulting dispersion is coated on a glass plate. when dry the coated plate is examined for optical homogeneity. The eflective aromatic ketones all give practically homogeneous gels in concentrations of from about 7 to about 20 grams of ketone per 100 grams of gelatin. Outside this range of solubility, the efllcacy of the aromatic ketones falls on very rapidly.

The majority of cyanine dyes which are supersensitized by the aromatic ketones are characterized by the fact that the dyes produce two types of sensitization depending upon condition Such different types of sensitization are described by Leermakers, Carroll and Staud, .J. Chem. Physics, 5, 878 (1937) and by G. Schwarz-Sci. et Ind. Phot. 10, 233 (1939). When a cyanine dye of this type is used as asensitizer in low concentration, it exhibits a sensitizing maximum displaced about 20 to 50 mu toward the red from the absorption maximum in ethyl alcohol so1ution. On increasing the concentration of the dye, or upon digesting the emulsion containing the dye in the lower concentration, or both, a second maximum of sensitization develops at longer wavelengths, accompanied by an increase in total optical sensitization. In some cases a decrease in sensitivity at the first maximum can be detected. These phenomena are consistent with the hypothesis of two states of the sensitizing dye in an equilibrium which is controlled by concentration. The aromatic ketones favor the formation of a second maximum. The increase in sensitivity apparently corresponds to increased conversion of the dye to the state corresponding to the second maximum of sensitization. In some cases the efiect appears to correspond to a more complete conversion than has ever been previously obtained, and in any case the long wavelength sensitivity is better than can be obtained from the same concentration of dye without the aromatic ketone.

The following are exemplary of the cyanine dyes which can be supersensitized in accordance with our invention: 3,3',9-triethylthiacarbocyanine (iodide) 3,3'-diethyl-9-methylthiacarbocyanine (bromide) 3,3'-diethyl 9 methylselenacarbocyanine (bromide) 3,3'-diethyl- 9-methyl -4,5,4',s' dibenzthiacarbocyanine (chloride) 3,3'-dimethyl- 9 -ethyl -4,5,4',5' -dibenzthiacarbocyanine (chloride) A 3,3'-diethyl -9- phenyl-4,5,4',5'-dibenzthiacarbocyanine (chloride) 3,3',9 triethyl 5,5 dichlorothiacarbocyanine (bromide) 3,3'-diethyl-9-methyl 5,5 dichlorothiacarbocyanine (bromide) 3,3'-dimethyl-9-ethyl cyanine (bromide) 1,1'-diethyl-2,2'-cyanine (iodide) 3,1'-diethyl-4,5-benzthia-2'-cyanine (bromide) 2,1'-diethyl-6'-methoxythia 2'-cyanine (iodide) The effect of the aromatic ketones is most pro- 5,5' dichlorothiacarbo- The eifect of the aromatic ketones is as'raeso rhodanine and 3- ethyl-- 5 [(3-ethyl-5-methyl- 2(3) -1,3,4-thiadiazolylidene) ethylidene] rhodanine are typical merocyanines which respond readily to the action of the aromatic ketones. especially marked with complex merocyanine dyes, such as produce the optimum sensitizing effect.

are described in the copendln application of Leslie G. S. Brooker, Serial No. 316,002, filed January 28, 1940, e. g. merocarbocyanine dyes or the following general formula: 1

o o ,z. N-R NR" methine group, R repreunsubstituted alkyl group,

represent alkyl or aryl groups, subunsubstituted, and Z represents the wherein L represents a sents a substituted or R and Rf stituted 0r non-metallic atoms necessary to complete a heterocyclic nucleus, such as used in cyanine dyes, e. g. benzothiazole, benzoxazole, fi-naphthothiazole, etc.

The sensitizing dyes can be employed in any desired concentration. Ordinarily from 10 to 30 mg. of dye per liter of emulsion will suflice to The methods of incorporating sensitizing dyes in emulsions are well known to those skilled in the art. Ordinarily, it is preferable to dissolve the dye in a water-miscible solvent, such as methanol, before incorporating in the emulsion. Ethyl alcohol or acetone may be used when the solubility of the dye in methanol is very low.

nounced' with the less soluble merocyanme dyes.

The amount of the aromatic ketone used is not critical. Usually the full supersensitizing effect is developed at a concentration of from 1 to 2 grams per liter of emulsion, but amounts up to the point where the ketone separates out on drying the emulsion can be used without bad eil'ects: that may be 10 or more grams per liter of emulsion. The aromatic ketones can be added with, before, or after the sensitizing dye or dyes. The aromatic ketones are preferably, but not necessarily, diluted with a water-miscible solvent, such as methanol, before incorporation in'the emulsion.

.The following examples will serve to illustrate results obtained in accordance with our invention.

Example 1 Red Minus blue p-Methoxyacetophenone Fog Speed Gamma Speed Gamma None 1.50 630 1. 49 .04 2.lig./liter -3l5 1.27' 830 1.36 .05

Exdmiile in 7 Red Minus blue p-Methoxyaoetcphe- Fog Speed Gamma Speed Gamma 1. None 52.5 1.40 276 1.40 2. p-Methoxyacetophenone 87 l. 23 355 l. 26 05 Red Minus blue Bensal acetone Fog Speed Gamma Speed Gamma None 130 1.44 045 1.45 .11 2.5 g./liter 340 1,30 830 l. 45 .08

. Example 1b To a last negative gelatino-silver-bromio'dide developing-out emulsion espectrally sensitized as in Example 1, was added o-hydroxyacetophenone. The emulsion was exposed as in Example 1, with and without the addition.

Rad Minus blue o-Hydroxyaceto- F0 phenone g Speed Gamma Speed Gamma None 150 l. 63 740 l. 01 17 2.5 g./liter 310 l. 38 725 l. 45 39 Example 2 filter.

Clear Minus blue p-Metlioxyaoeto- F phenone 08 Speed Gamma Speed Gamma 1. None 910 1.26 326 1.38 .06 2. 5 g.llite1- 1,100 1.27 380 1.30 .07

Example 3 A slower high contrast gelatino-silver-bromiodide developing-out emulsion was sensitized with 3,3 diethyl 9 methylthiacarbocyanine bromide (20 mg./1iter of emulsion), and to the spectrally sensitized emulsion was added p-methoxy acetophenone. The emulsion was exposed as in Example 1.

M h w h Red Minus blue I p at oxyaoe p e- I none Fog Speed Gamma Speed Gamma 1. None 13.3 2.15 118 2.75 .04 2 2.5 g./liter 32.5 2.45 162 2.54 .04

Example 4 A fast gelatino-silver-bromiodide developingout emulsion was sensitized with 3,3',9-triethylthiacarboncyanine iodide (20 mg./liter or emulsion), and to the spectrally sensitized emulsion was added p-methoxy acetophenone. The emulsion was exposed with and without the addition of the p-methoxy acetophenone as'in Example 1.

Our invention is primarily directed to the customarily employed geatino-silver-halide developing-out emulsions for development to blackand-white images, such as gelatino-silver-chloride, gelatino silver chlorobromide, gelatinosilver-bromide and gelatino-silver-bromiodide developing-out emulsion.

Emulsions prepared in accordance with our invention can be coated in the usual manner upon any desired support such as cellulose nitrate support, cellulose acetate support, polyvinyl acetal resin support, metal support or paper support.

The accompanying drawing further illustrates the super-sensitizing effect obtained with two of our new combinations in gelatino-silver-bromiodide emulsions. Each figure or the drawing is a diagrammatic reproduction of ,two spectrograms. In each figure, the sensitivity of the emulsions containing only the sensitizing dye is represented by the broken-line curve, while the sensitivity of the same emulsion containing the sensitizing dye in combination with an aromatic ketone is represented by the solid-line curve. Inasmuch as the aromatic ketones have little or no sensitizing effect on gelatino-silver-bromiodide emulsions, no spectrogram for the emulsion containing the aromatic ketone alone is shown.

In Figure 1, curve A represents the sensitivity of a fast, negative gelatino-silver-bromiodide developing-out emulsion sensitized with 3,3'-diethyl -9-methyl selenacarbocyanine bromide (in a concentration of 20 mg. per liter of emulsion), and curve B represents the sensitivity of the same gelatino-silver bromiodide emulsion containing 3,3- diethyl 9 methyl selenacarbocyanine bromide (20 mg. per liter of emulsion) plus p-methoxy acetophenone, in a concentration of 2.5 g. per liter of emulsion.The supersensitizing effect of the aromatic ketone is apparent.

In Figure 2, curve C represents the sensitivity of a fast, negative gelatino-silver-bromiodide emulsion containing 3,3-diethyl-9-methyl selenacarbocyanine bromide (in a concentration of 20 mg. per liter of emulsion), and curve D represents the sensitivity of the same gelatino-silverbromiodide emulsion containing 3,3'-diethyl-9- methyl selenacarbocyanine bromide (20 mg. per liter of emulsion) plus o-hydroxy acetophenone, in a concentration of 1.25 g. per liter of emulsion. The supersensitizing effect of the aromatic ketone is apparent.

Merocyanine dyes are described in U. S. Patent 2,078,233, dated April 27, 1937, in U. S. Patent 2,170,803, in U. S. Patent 2,165,338, dated July 11, 1939, in U. S. Patent 2,263,757, dated November 25, 1941, and in the copending application Serial No. 316,002 filed January 27, 1940, of Leslie G. S. Brooker, said copending application describing the more complex dyes.

What we claim as our invention and desire to be secured by Letters Patent 0! the United States is:

1. A photographic silver halide emulsion spectrally sensitized with a sensitizing dye selected from the group consisting of cyanine and merocyanine dyes, said emulsion containing, as a supersensitizer in a concentration 01' not more than grams per liter of emulsion, an aromatic ketone selected from those represented by the following general formula:

wherein R represents an aryl group, R represents an organic radical selected from the group consisting of alkyl groups and aryl groups, and n and 1:. each represent a positive integer or from 1 to 2 except that n and n do not both represent 2 at the same time.

2. A process for preparing a sensitized photographic silver halide emulsion comprising incorporating in a photographicsilver halide emulsion a sensitizing dye selected from the group consisting of cyanine and merocyanine dyes and not more than 10 grams aromatic ketone selected from those represented by the following general formula:

wherein R represents an aryl group, R represents an organic radical selected from the group consisting' of alkyl groups and aryl groups, and n and n' each represent, a positive integer of from 1 to 2 except that n and 11' do not both represent 2 at the same time.

3. A trally sensitized with a sensitizing dye selected from the group consisting of cyanine and merocyanine dyes, said emulsion containing, as a supersensitizer in a concentration of not more than- 10 grams per liter of emulsion, an aromatic ketone selected from those represented by the following general formula:

wherein It represents an aryl group of the benzene series, R represents an organic radical selected from 'the group consisting of alkyl groups and aryl groups of the benzene series, and n and n each represent a positive integer of from 1 to 2 except that n and n the same time.

4. A process for preparing a sensitized photographic silver halide emulsion comprising ins, corporating in a photographic silver halide emulsion 9. sensitizing dye selected from the group consisting of cyanine and merocyanine dyes and not more than 10 grams per liter of emulsion of an aromatic ketone selected from those represented by the following general formula:--

wherein R represents an aryl group of the henzene series, R' represents an organic radical selected from the group consisting of alkyl groups and aryl groups of the benzene series, and n and n each represent a positive integer of from 1 to 2 except that n and n do not both represent 2 at the same time.

5. A photographic silver halide emulsion for development to black-and-white images spectrally sensitized with a sensitizing dye selected from the group consisting oi cyanine and merocyanine dyes, said emulsion containing, as a supersensitizer in a concentration of not more than 10 grams per liter of emulsion, an aromatic ke- Per liter of emulsion of an 2 except that photographic silver halide emulsion specdo not both represent 2 at g second maximum of not more than 10 tone selected from those represented R(CH=CH),i-i (CH=OH)"-i-R' wherein R represents an aryl group of the benzene series, R represents an organic radical selected from the group consisting of alkyl groups and aryl groups of the benzene series, and n and 11. each represent a positive integer of from 1 to n and u do not both represent 2 at the same time. a

6. A process for preparing a supersensitized photographic silver halide of thetype employed for development to black-and-white images comprising incorporating in the emulsion a sensitizing dye selected from the group consisting of cyanine and merocyanine dyes and not more than 10 gram per liter of emulsion of an aromatic ketone selected from those represented by the following general formula:

wherein-R represents an aryl group of the benzene series, B represents an organic radical selected from the group consisting of alkyl groups and aryl groups of the benzene series, and n and n' each represent a positive integer of from 1 to 2 except that n and n do not both represent 2 at the same time.

7. A photographic silver halide emulsion for development to black-and-white images spectrally sensitized with 'a cyanine dye which produces maximum sensitivity in the emulsion at one concentration and at a higher concentration, or upon digestion of the emulsion containing the dye at the lower concentration, produces a second maximum at a wavelength longer than that of the first maximum, said emulsion containing, as a supersensitizer in a concentration of not more than 10 grams per liter of emulsion, an aromatic ketone selected from those which are represented by the following general formula:

wherein' R represents an aryl group of the henzene series, R represents an organic radical selected from the group consisting of alkyl groups and aryl groups of the benzene series, and n and n each represent a positive integer of from 1 to 2 except that n and u do not both represent 2 at the same time.

8. A photographic gelatino-silver-haiide emulsion for development to black-and-white images spectrally sensitizedwith a cyanine dye which produces maximum sensitivity in the emulsion at one concentration and at a higher concentration, or upon digestion of the emulsion containing the dye at the lower concentration, produces a at a wavelength longer than that of the first maximum, said emulsion containing,. as a supersensitizer in a concentration grams per liter of emulsion, an aromatic ketone selected from those which are represented by the following general formula:

. Y Certificate of Correction Patent N 0. 2,373,659.

It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows: Page 1, second column, lines 19 to 23, strike out the formula and insert instead. 7

, on I o O page 2, first column, line 62,' before 3,3-dietl 1yl insert 3,8,9-friethgl-4,5,4',5-rlibenzthakzcarbocyanine (chlortde); and that the said Letters Patent should be read with these corrections therem that the same may conform to the Patent Office.

record of the case in the Signed and sealed this 16th day of October, A. D. 1945.

[SEAL] LESLIE FRAZER,

First Assistant Commissioner of Patents.

- April 17, 1945. BURT H. CARROLL ET AL.

wherein R and R each 'of from about '1 to 2 except that n and 11' do not both represent 2 at the same time, said ketone having a solubility in gelatin of from about '7 to about 20grams of ketone per 100 grams or gela 9. A photographic gelatino-silver-halide emulsion for development to black-and-white images spectrally sensitized with a cyanine dye which produces maximum sensitivity in the emulsion at one concentration and at a higher concentration, or upon digestion of the emulsion containin: the dye at the lower concentratio produces a second maximum at a wavelength longer than that or the first maximum, said emulsion containing, as a supersensitizer in a concentration or not more than 10 grams per liter of emulsion, an aromatic ketone selected from those which are represented by the following general formula:

represent an allqrl group of the formula CnH2n+i wherein n represents a positive integer and the OR group is in one of the positions which are ortho'and para to the II -CR group, said ketone having a solubility in gelatin about 20 grams of ketone per 100 grams or gelatin.

10. A photographic gelatino-silver-halide emulsion for development to black-and-white images spectrally sensitized with a cyanine dye which produces maximum sensitivity in the emulsion at one concentration and at a higher concentration, or upon digestion of the emulsion containing the dye at the lower concentration, produces a second maximum at a wavelength longer than that of the first maximum, said emulsion containing, as a supersensltizer in a concentration of not more than grams per liter of emulsion, an aromatic ketone selected from those which are represented by the following general formula:

spectrally sensitize wherein 3 re ts an alkyl group 0! the formula Celina wherein n represents a positive integer.

n. A photographic gelatino-sllver-halide emulsion for development to black-and-white images d with a cyanine dye which produces maximum sensitivity in the emulsion at one concentration and at a higher concentration, or upon digestion of the emulsion containing the dye at the lower concentratio produce a second maximum at a wavelength longer than that of the first maximum, said emulsion containing, as a supersensitizer in a concentration or not more than 10 grams per liter 0! emulsion, an aromatic ketone selected from those which are represented by the following general lormula:

wherein It represents an allryl group or the formula CnH2n+i wherein 11 represent a positive integer.

12. A photographic gelatino-silver-halide emulsion for development to black-and-white images spectrally sensitized with a cyanine dye which produces maximum sensitivity in the emulsion at one concentration and at a higher concentration, or upon digestion of the emulsion containing the dye at the lower concentration, produces a second maximum at a wavelength longer than that 0! the first maximum. said emulsion containing. as a supersensitizer in a concentration of not more than 10 grams per liter of emulsion, an aromatic ketone selected from are represented by the following general formula:

0 ll RCR wherein R represents an aryl group of the benzene series and R represents an organic radical selected from the group consisting of alkyl groups and aryl groups or the benzene series.

BURT H. CARROLL. JOHN SPENCE.

those which 

